JPH0477774A - Developing device - Google Patents

Abstract

PURPOSE:To restrain the deterioration of image density and the increase of fogging on a paper and to prevent image quality from being deteriorated even in the case that a developing device is used for a long time by fixing the range of the desired radius of curvature at a semicircle-like cross section part in the press-contact part of a thin layer forming means for developer. CONSTITUTION:A blade 16 is always pressed by plural compression springs 22 by setting a rotating shaft 21 as a fulcrum so that the tip part (tip 162) thereof presses the surface of a developing roller 12 by proper force. Besides, when the radius of curvature of the tip 162 at a part which abuts on the develop ing roller 12 is set to be too small, the electrostatic charge quantity of toner becomes small and the fogging on a transfer paper is increased. When it is set to be too large, the layer thickness of the toner on the developing roller 12 becomes too thin and the image density is deteriorated. In order to obtain an excellent image whose image density is >=1.2 and fogging generation probabil ity is <=2%, the ratio of the radius R(mm) of the developing roller 12 and the radius(mm) of curvature of the tip 162 is set to be within the range of 2<=R/(r)<=20.

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a developing device for visualizing an electrostatic latent image formed on an electrostatic latent image holder in an electrophotographic device or an electrostatic recording device. (Prior Art) One of the developing methods using a one-component developer is the pressure developing method.
It has been known. One feature of this pressure development method is that by pressing the tip of something called a blade against the surface of the developing roller, the friction imparts an electric charge to the toner, forming a thin layer of toner on the surface of the developing roller. There is. Therefore, it has many advantages such as no magnetic material is required, the device can be simplified and miniaturized, and it is easy to use colored toner. Furthermore, in developing devices that employ this pressure development method, resin or rubber elastic material is usually used for the pressure contact part of the blade, and the purpose of this pressure contact part is to form a toner layer of uniform thickness on the surface of the developing roller. It is often made into a rounded shape. (Problems to be Solved by the Invention) However, when the shape of the pressure contact portion of the blade is rounded in this way, the radius of curvature becomes a factor that directly affects the quality of the development process. The present invention was made to solve such problems,
Based on the relationship between the radius of the developing roller and the average particle radius of the developer, the range of the desirable radius of curvature of the semicircular cross-section of the pressure contact part of the developer thin layer forming means is determined, and this prevents a decrease in image density and blade blur on the paper. The object of the present invention is to provide a developing device that suppresses the increase in image quality and does not cause deterioration in image quality even after long-term use. [Structure of the invention] (Means for solving the problem) In order to achieve the above object, the developing device of the first invention has the following features:
A developing roller disposed opposite to the electrostatic latent image holder, and a developer thin layer forming means for forming a thin developer layer on the surface of the developing roller. In a developing device that visualizes an electrostatic latent image by bringing a thin layer of developer close to or in contact with an electrostatic latent image holder, the thin developer layer forming means includes a half-layer that is pressed against the surface of the developing roller with the developer sandwiched therebetween. It has a pressure welding part with a circular cross section, and the radius of curvature of the semicircular cross section of the pressure welding part is r (mm),
When the radius of the developing roller is R (mm), it is characterized by satisfying the following: 2≦R/r≦20. In order to achieve the above object, the developing device of the second invention has the following features:
A developing roller disposed opposite to the electrostatic latent image holder, and a developer thin layer forming means for forming a thin developer layer on the surface of the developing roller. In a developing device that visualizes an electrostatic latent image by bringing a thin layer of developer close to or in contact with an electrostatic latent image holder, the thin developer layer forming means includes a half-layer that is pressed against the surface of the developing roller with the developer sandwiched therebetween. It has a pressing part with a circular cross section, and the radius of curvature of the semicircular cross section of the pressing part is "(mm),"
If the average particle radius of the developer is rt (mm), it is characterized by satisfying the following: 00≦r/rt≦1000. (Function) In the present invention, the desirable range of the radius of curvature of the semicircular cross-sectional portion of the pressure contact portion of the developer thin layer forming means is determined from the relationship between the radius of the developing roller and the average particle radius of the developer. It is possible to realize a developing device that suppresses a decrease in image density, an increase in edge blur on paper, and does not cause deterioration in image quality even after long-term use. (Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing the overall structure of a contact type component nonmagnetic developing device (hereinafter simply referred to as a developing device) according to an embodiment of the present invention. As shown in the figure, this developing device 10 uses non-magnetic toner (hereinafter simply referred to as toner) as a developer on an electrostatic latent image formed on the surface of a photoreceptor drum 11, which is an electrostatic latent image holder. ) 2, a toner container 13 containing toner A, and a mixer 4, which stirs the toner A in this toner container 13. , a toner supply roller 15 that supplies toner A in the toner container 13 to the developing roller 12, and a developing roller 1.
The main part thereof is composed of a blade 16 which is a thin developer layer forming means for forming a thin toner layer on two surfaces. Next, the developing process in this developing device 10 will be explained. The toner A contained in the toner container 13 is mixed with the mixer]
4, the toner is sent toward the toner supply roller 15, and further supplied to the developing roller 12 by the toner supply roller 15. Here, the toner A is negatively charged due to friction with the surface of the rotating developing roller 12, is electrostatically attracted to the surface of the developing roller 12, and is transported. After this,
The toner A attached to the surface of the developing roller 12 is removed by the blade 1.
6 regulates the amount of toner conveyed and becomes a thin layer, and at the same time, it is triboelectrically charged again due to friction with the developing roller 12 and blade 16, and is conveyed as a dense toner layer. Thereafter, the toner A adhering to the surface of the developing roller 12 is transferred onto the electrostatic latent image on the surface of the photoreceptor drum 11 due to contact with the photoreceptor drum 11 . This makes the electrostatic latent image visible. The toner A on the surface of the developing roller 12 that has not been transferred scrapes through the recovery blade (Mylar film) 17 and returns to the toner container 13 . By the way, in this embodiment, since a reversal development method using a negatively charged organic photoreceptor drum 1 is adopted, a negatively charged toner is used as the toner A, and the blade 16
A material that easily charges the toner A negatively is used. Also, the surface potential of photoreceptor drum] 1 is -550
In contrast, -200 V is applied to the metal shaft 12a of the developing roller 12 via a protective resistor as a developing bias potential. Further, the developing roller 12 is always 1 to 5 mm from the surface of the photoreceptor drum 11.
The photosensitive drum 11 rotates at a speed approximately 1 to 4 times as high as the rotation speed of the photosensitive drum 11 while having a contact width (developing nip) of approximately 100 mL. In addition, if toner A falls from the developing roller 12 for some reason in the above-mentioned developing process, it will stain the inside of the main unit or the transfer paper, so in this embodiment, the toner A is made of a plasticizer or the like that welds the toner A. A toner welding member 18 is attached to the lower part of the developing device 1o. Also, this allows
Even if the developing device 1° is placed upside down, scattering of toner A can be prevented. The above blade 16 is attached to a first blade holder 16a1.
It is supported by the device main body by a spacer 16b and a second blade holder 16c. Reference numeral 19 denotes a baffle plate attached to the first blade boulder 16g to sandwich a foamed material 20 made of maltbrene or the like between it and the back surface of the blade 16. By sandwiching the foamed material 20 between the baffle plate 19 and the back surface of the blade 16 in this manner, leakage of toner A from the toner container 13 and vibration of the blade 16 are prevented. Also, this blade 16 has a tip portion (chi-1;'
162), a plurality of compression springs 2 are installed around the rotating shaft 21 so as to press the surface of the developing roller 12 with an appropriate force.
2, it is constantly energized. These compression springs 2
Since the spring constant of the blade 16 is lower than that of the blade 16 (thin plate spring 161), even if the tip 162 of the blade 16 is worn, the pressing force thereof is hardly affected. Next, the above-mentioned developing roller 12 will be explained in detail. FIG. 2 is a perspective sectional view showing the developing roller 12. The characteristics required of the developing roller 12 are that it has "conductivity and elasticity". The simplest configuration that satisfies this requirement is, for example, one in which the outer periphery of a metal shaft is covered with a conductive rubber roller. However, in the developing system of this embodiment, the toner is conveyed while being pressed against the surface of the developing roller 12. Therefore, surface smoothness is required. Therefore, in the developing roller 12 of this embodiment, an elastic layer 12b made of, for example, conductive silicone rubber or urethane rubber is provided on the outer periphery of the metal shaft 12a. Conductive layer 12
c is provided to create a two-layer structure. The elastic layer 12b may be conductive or non-conductive, but it is preferable to use a conductive layer in consideration of the possibility that the conductive layer 12c may be peeled off or damaged. The rubber hardness of the elastic layer 12b is a factor that directly affects the load and torque of the developing roller 12 to obtain an appropriate nip between the developing roller 2 and the photoreceptor drum 11. In addition, Jl5K6301 may be damaged during packaging or when left unattended for a long time.
Regarding the permanent strain shown in , it is known that if the permanent strain exceeds 10%, uneven rotation period of the developing roller will occur in the image, so the compressive strain of the elastic layer 12b should be 10% or less, preferably 5% or less. There must be. Regarding the relationship between rubber hardness and permanent set, there is generally a tendency that the higher the rubber hardness, the smaller the permanent set, so the balance between the materials and each other is important. Also, what cannot be ignored here is the speed at which the surface of the developing roller 12 recovers from distortion caused by pressure contact with the photoreceptor drum 11 and the blade 16. If development is performed with distortions remaining, uneven density, blurring, etc. are likely to occur, resulting in a significant deterioration in image quality. As a countermeasure against this problem, a method may be considered in which the photosensitive drum 1 and the blade 16 are kept at a position apart from the developing roller 12 before the developing device 10 is installed in the main unit, such as during packaging. However, after the developing device] 0 is attached to the main unit and the toner is stored in the toner container 13, the photosensitive drum 11 can be retracted to a position away from the developing roller 12 when not in operation, but the blade 16 also has the role of damming up the toner in the toner container 13, so it cannot be moved from its fixed position. Therefore, regarding the deformation of the surface of the developing roller 12 due to the pressure contact of the blade 16, the time from when the developing roller 12 starts rotating until the actual development starts when the main unit starts the first print from the ready state. It is required that the residual strain is recovered to 10 μm or less within, for example, 10 seconds. FIG. 3 is a graph showing the relationship between residual strain and recovery time for three types of developing rollers with different film thicknesses T (μm) of the conductive layer 12c. From the figure, the residual strain (μm) depends on the thickness T (μm) of the conductive layer 12C if the elastic layer 12b is the same, and if the thickness T of the conductive layer 12c is 100 μm or less, the residual strain (μm) depends on the thickness T (μm) of the conductive layer 12C. “
It can be seen that the condition that the residual strain is 10 μm or less in 10 seconds or less is satisfied. In addition, the conductive layer 12c can be directly applied to toner or the photoreceptor drum 11.
Since this is the surface that comes into contact with the surface, the surface smoothness is limited to the maximum surface roughness as long as it does not contaminate the toner or the surface of the photoreceptor drum 11 by seeping out plasticizers, sulfurizing agents, process oil, etc. It is desirable that the thickness is 3 μm or less. If it exceeds this range, uneven patterns on the surface tend to appear in the image. A method for achieving a smoothness of the conductive layer 12c with a maximum surface roughness of 3 μm or less is to apply the conductive layer 12c with a sufficient thickness on the elastic layer 12b, and then use post-processing (polishing) to obtain a smoothness of the conductive layer 12c. One possible method is to finish the outer diameter and surface roughness, but this method increases the cost. Therefore, a method of finishing without requiring post-processing is desired, and for this purpose, the surface roughness of the elastic layer 12b, the film thickness of the conductive layer 12c, and the viscosity of the paint for forming the conductive layer 12c are optimally selected. Must. That is, the lower the viscosity of the paint and the greater the surface roughness of the elastic layer 12b, the thicker the conductive layer 12c must be. teeth,
Depending on the method of applying the paint to the surface of the elastic layer 12b, the viscosity of the same paint must be varied by changing the amount of dilution. FIGS. 4 to 6 show typical methods of applying the conductive layer paint. FIG. 4 shows a spray coating method, FIG. 5 shows a dipping coating method, and FIG. 6 shows a knife coating method. The viscosity of the paint in each method is spray method <dipping method ≦ Naifetsu method,
Smoothness of the surface of the pre-electroconductive layer 12c (maximum surface roughness 3 μm)
The paint film thickness T (μm) required to achieve this is T≧5XRz in the spray method, and T≧5XRz in the dipping method and knife edge method, assuming that the maximum surface roughness of the elastic layer 12b is Rz (μm). is possible if T≧3XRz is satisfied. Therefore, the film thickness T (μm) of the conductive layer 12 is determined by the time t s (see) from the start of rotation of the developing roller 12 to the start of development when the main unit starts the first print from the ready state. If, 0≦

[If 3XRz≦T≦100 is satisfied when S≦10, a high-quality image can be maintained and a low-cost developing roller 12 can be realized. Furthermore, the elongation of the material of the conductive layer 12c itself cannot be ignored here. That is, if this is less than 50%, the conductive layer 12c cannot follow the elastic deformation of the elastic layer 12b,
Cracks are particularly likely to occur at both ends where elastic deformation is large. Furthermore, the elongation of the material of the elastic layer 12b and the conductive layer 12c
If the difference between the elongation of the material itself and the elongation of the material itself does not satisfy 200 or less, that is, if each elongation is taken as LeSLl, then ILe-Lit≦200, cracks will similarly occur in the conductive layer 12c, and one of the developing rollers 12 Density unevenness within the rotation is likely to occur. Furthermore, since the conductive layer 12c charges the toner negatively, it is required to be made of a material that is easily triboelectrically positively charged, and must also have excellent toner transportability. As a characteristic of the developing roller 12, the resistance between the metal shaft 12a and the surface of the conductive layer 12c is determined by the development bias power supply and the metal shaft 1.
By conducting a development experiment with a resistor having an arbitrary resistance value interposed between the developing roller and 2a, a correlation between the potential of the developing roller surface, the resistance value, and the image was obtained. The results are shown in FIG. Note that the voltage of the developing bias power supply at this time was -200V. As is clear from the figure, at a resistance value of 1X10'Ω or more, the surface potential of the developing roller during development shows different values for a white solid image and a black solid image, and for a white solid image, a white background latent image appears. In the case of a solid black image, the potential tends to approach the potential of a solid black latent image. In other words, in an image having a large image area, the potential difference between the latent image potential of the image area and the surface potential of the developing roller becomes small, resulting in an image with low density. Since the surface potential approaches the white background latent image potential, the potential difference with the image area increases, resulting in thin lines becoming thicker, resulting in an image with no sharpness. Such fluctuations in the surface potential of the developing roller are caused by the current flowing through the resistor during development. That is, during black solid development, negatively charged toner is transferred from the developing roller 12 to the photosensitive drum 11, so that a current flows from the developing roller 12 toward the developing bias power source. During white solid development, the surface charge of the photosensitive drum 11 is removed by the developing roller 12, and a current flows from the developing bias power source toward the developing roller 12. Such a current causes a potential difference between both ends of the resistor, causing the above-mentioned fluctuation in the surface potential of the developing roller. This tendency was particularly noticeable when the resistance value was I x 1.0"Ω or more. From this, the actual resistance value between the metal shaft 12a and the conductive layer 12c is 1 x 10"Ω or less,
It was confirmed that good images can be obtained preferably when the resistance is 1×10 7 Ω or less. However, since there is actually an adhesive layer, a brimer treatment layer, etc. between the metal shirt 12a and the elastic layer 12b,
It needs to be lower than this. In this example, good results were obtained by setting the resistance values of the elastic layer 12b and the conductive layer 12c to 1×10 6 Ω·0 m or less, respectively. From the above, in the developing roller 12 of this embodiment, the elastic layer 12b has a rubber hardness (JIS-A) of 35' or less, an elongation of about 250 to 500%, and a resistance value of lXl0'Ω·0.
Conductive silicone rubber or conductive urethane rubber with a diameter of less than m is used, and the conductive layer 12C is a conductive polyurethane paint, such as "Subarex" manufactured by Nippon Miractron ■, with a resistance value of 104 to 105 Ω·cm and an elongation of 100 to 400.
% was used. As a result, the rubber hardness of the developing roller 12 as a whole was approximately 30 to 50'. Furthermore, by forming a conductive layer 12c with a film thickness of about 50 to 100 μm by spray coating on the elastic layers 1 and 2b with a surface roughness of 5 to 10 μm, a developing roller 12 with a maximum surface roughness of 3 μm is realized. did it. As a result, the developing roller 12 has a good distortion recovery speed and can obtain high-quality images.
I was able to realize this. Next, the blade 16 and its surroundings in the developing device 10 of this embodiment will be explained. FIG. 8 is a perspective view showing details of the blade]6. As shown in the figure, this blade] 6 is a thin plate spring 16.
A tip 16 having a semicircular cross section made of a rubber elastic body or resin such as silicone rubber or urethane is attached to the tip of the tip 1.
2 is mounted in an elongated direction, and a sealing material 163 made of urethane foam or the like is attached to both ends thereof. The thin plate spring 161 is made of a stainless steel or copper-based spring material, and is preferably made of beryllium copper, phosphor bronze, nickel silver, etc., which have a smaller spring constant than stainless steel, since a large spring constant causes faster wear of the tip 162. By using a copper-based spring material, wear of the tip 162 can be minimized. Note that in this example, a phosphor bronze plate was used from a cost perspective, and the plate thickness was Q, 2 mm, but it was satisfactory if it was within the range of O, 1 to 2.0 mm. Since the sealing material 163 has a cross section thicker than the height of the tip 162, it can reliably seal the movement of toner toward both ends when the tip 162 is pressed against the developing roller 12. By the way, in this blade 16,
If the chip 162 is not firmly pressed against the surface of the developing roller 12, uneven formation of a thin toner layer will occur.
The viscosity of the contact portion between the developing roller 12 and the developing roller 12 is required. Experiments have shown that if the straightness is 50 μm or less, unevenness in the formation of a thin toner layer can be ignored. However, the accuracy of the blade disclosed in the above-mentioned US Pat. No. 3,152.012, etc. is limited to 100 μm. Therefore, in this embodiment, the blade 16 is constructed by mounting a chip 162 having a semicircular cross section on a thin plate spring 161. As a result, even if the accuracy of Chi-Tub 162 is 100
Even if the thickness is μm, the elasticity of the thin plate spring 161 makes it possible to easily and reliably form an even toner layer on the surface of the developing roller 12. Further, in the blade 16 in this embodiment, the ninth
As shown in the figure, the chip 162 is mounted from a position dl away from the tip of the thin plate spring 161. That is, the tip portion of the thin plate spring 161 is used for holding and positioning when mounting the chip 162 on the thin plate spring 161 by molding or adhesion. This makes it possible to improve the mounting accuracy of the thin plate spring 161 in the lateral direction, as well as the accuracy in the tangential direction with respect to the developing roller 12. Note that if di is too large, the pressure caused by the toner flow may cause defective toner layer formation, so it is appropriate to set di to be about 0.5 to 5 mm. The optimal thickness is desirably about 0.5 to 2 mm. Furthermore, there are portions at both ends of the thin plate spring 161 in the longitudinal direction where the chip 162 is not mounted. The above-described seal member 163 is attached to this portion. In other words, the length Lp of the chip 162 in the longitudinal direction is shorter than the length Lc of the thin plate spring 161 by d2 d3. The length of d2 + d3 needs to be at least 2 mm on each side considering sealing performance, but if it is too long, the developing device 10 itself will become large, so the length should be 4 to 30 mm.
The thickness is preferably about 4 to 20 mm. Further, the length Lp of the chip 162 at this time is greater than the effective development width of the developing roller 12, and the length Lc of the thin plate spring 161 is equal to the width of the developing roller 12 or the side seal of the developing roller 12 (not shown). ). Furthermore, if the radius of curvature of the chip 162 in the portion that contacts the developing roller 12 is too small, the amount of toner charge will be small and fog on the transfer paper will increase; if it is too large, the width of contact with the developing roller 12 will be large. The required rotational torque increases accordingly, and the toner layer thickness on the developing roller 12 becomes too thin, resulting in a decrease in image density, so it is necessary to keep it within an appropriate range. It has been confirmed through experiments that the range of the radius of curvature r that is desirable for performance in the chip 162 depends on the radius of the developing roller 12 and the average particle radius of the toner. Figure 10 shows the radius R (mm) and nap of the developing roller 12]
62 is a graph showing the relationship between the ratio of the radius of curvature r (mm) of No. 62 and the image quality (solid density and probability of fogging). In this graph, the white circle indicates the radius R of the developing roller 12.
is 6 mm, the black circle indicates that the radius R of the developing roller 12 is 20 mm.
The case of mm is shown respectively. As is clear from this graph, in order to obtain a good image with an image density of 1.2 or more and a fogging probability of 2% or less, the value of the ratio (R/r) must be 2≦R/ r≦20 --------(1)
It was found that it is sufficient if it is within the range of . Furthermore, FIG. 11 is a graph showing the relationship between the ratio of the radius of curvature r (mm) of the chip 62 and the average particle radius of the toner rt (mm) and the image quality (solid density and probability of fogging). In this graph, white circles indicate the case where the average particle radius rt of the toner is 1.5 μm, and black circles indicate the case where the average particle radius rt of the toner is 7.5 μm. As is clear from this graph, as above, in order to obtain a good image with an image density of 1.2 or more and a fogging probability of 2% or less, the ratio (r/r t ) must be
The value of is 100≦r/"1≦1000...(2)
It was confirmed that it is sufficient if it is within the range of . Note that the above equations (1) and (2) are applied only to the blade 16 in which the portion in pressure contact with the developing roller 12 has a semicircular cross section, and other configurations of the blade 6 are applicable. It is not affected by the above differences. Next, the toner supply roller 15 will be explained. The toner supply roller 15 has two roles: supplying toner to the developing roller 12 and scraping off residual toner on the developing roller 12 after development. This toner supply roller 15 has a metal shaft 15a surrounded by a metal shaft 15a having a conductivity of 0.8Ω·cm or less and a density of 0.8Ω·cm or less. 045 g/cm2, number of cells 50-60 cells/
Soft polyurethane foam layer 1 of approximately 25 mm
．． 5 b. Further, the contact depth with respect to the developing roller 12 is about 0.2 to 1.0 mm, and the rotation speed is set to 1/2 to a constant speed in the opposite direction to the developing roller 12. A bias voltage having the same potential as that of the developing roller 12 is applied. Thus, according to the developing device of this embodiment, the developing roller 1
From the relationship between the radius R of 2 and the average particle radius rt of the toner, the range of the radius of curvature r that is desirable for performance in the tip 162 of the blade 16 is determined. It becomes possible to realize the developing device 10 that does not cause deterioration in image quality even after long-term use. In the above embodiments, a 1.2 g metal shaft was used as the support for the developing roller 12, but as long as the developing bias voltage can be supplied, it may be a conductive resin shaft, for example. In the type of developing roller that supplies power to the elastic layer 12c or the elastic layer 12b,
The support does not need to be electrically conductive and may be made of an insulating material. Further, the elastic layer 12b of the developing roller 12 and the conductive layer 1
Although conductive silicone rubber, urethane rubber, and conductive polyurethane paint have been cited as examples of the material 2c, the present invention is not limited thereto, and may be any material that satisfies the characteristics required for this developing device 10. Anything is fine. Further, although the blade 16 is supported at a position against the rotation of the developing roller]2,
It may be supported at the with position with respect to the rotation of. Further, in the above embodiments, a contact non-magnetic component developer is used, but the present invention is not limited to this, and for example, an AC or DC bias non-contact developer may be used. [Effects of the Invention] As explained above, according to the present invention, the desirable curvature of the semicircular cross-sectional portion of the pressure contact portion of the developer thin layer forming means is determined from the relationship between the radius of the developing roller and the average particle radius of the developer. By determining the range of the cliff diameter, it is possible to suppress a decrease in image density and an increase in edge blur on paper, thereby realizing a developing device that does not cause deterioration in image quality even after long-term use.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the overall structure of a developing device according to an embodiment of the present invention, FIG. 2 is a perspective sectional view illustrating the structure of a developing roller in the developing device shown in FIG. 1, and FIG. A diagram showing the relationship between the layer thickness of the conductive layer and the strain recovery speed, FIGS. 4 to 6 are t-th diagrams explaining the method of forming the conductive layer of the developing roller, and FIG. 7 is the developing roller. 8 is a perspective view showing the blade in the developing device of FIG. 1, and FIG. 9 is a diagram showing the correlation between the surface potential, resistance value, and image.
10 is a graph showing the relationship between the ratio of the radius of the developing roller to the radius of curvature of the chip and the image quality.
FIG. 11 is a graph showing the relationship between the ratio of the radius of curvature of the tip to the average particle radius of l·ner and the image quality. ]0...Developing device, ]1...Photosensitive drum, 12.
・Developing roller, 16...blade, ]6]...thin plate blade, ]62...chip. d1 Gandai Toshiba Corporation

Claims (2)

[Claims] (1) A developing roller disposed opposite to the electrostatic latent image holder, and a developer thin layer forming means for forming a developer thin layer on the surface of the developing roller, In a developing device that visualizes an electrostatic latent image by bringing the formed developer thin layer close to or in contact with the electrostatic latent image holder, the developer thin layer forming means is configured to bring the developer between the surface of the developing roller and the developer. The pressure contact part has a semicircular cross section that is pressed with the pressure contact part in between, and the radius of curvature of the semicircular cross section of the pressure contact part is r (mm), and the radius of the developing roller is R (
mm), a developing device that satisfies 2≦R/r≦20. (2) A developing roller disposed facing the electrostatic latent image holder, and a developer thin layer forming means for forming a developer thin layer on the surface of the developing roller, In a developing device that visualizes an electrostatic latent image by bringing the formed developer thin layer close to or in contact with the electrostatic latent image holder, the developer thin layer forming means is configured to bring the developer between the surface of the developing roller and the developer. has a press-contact part having a semicircular cross-section that is pressed with the press-contact part in between, and the radius of curvature of the semicircular cross-section of the press-contact part is r (mm), and the average particle radius of the developer is rt.
(mm), 100≦r/rt≦1000.